The spinal cord circuitry of the monkey is being examined following labeling of particular axonal systems by degeneration or autoradiographic methods. Ascending projections to the monkey thalamus from spinal cord or dorsal column nuclei are studied by electron microscope methods. The intrinsic circuitry of neurons of the thalamus of cat and monkey is analyzed by labeling local thalamic neurons by degeneration or autoradiographic methods.